This invention relates generally to sheet feeders of the stand alone type or the type used to feed sheets of varying sizes and thicknesses into other production equipment for processing. The feeder of this invention was first designed for sheets of paper, but it has been found to have much broader application. Accordingly, the term “sheet” as applied to the feeder of this invention is used herein to encompass not only paper, for which prior art feeders have been designed, but also such things as CDs, credit cards, labels, calendars, or any other object, generally on the order of a few thousandths of an inch to about ⅜ of an inch thick, and sufficiently flexible to flex on the order of 1/16 to ⅛ inch, that can be fed from a stack.
There are hundreds or even thousands of paper sheet feeders made for thousands of uses. Typically, high speed sheet feeders are used when it is desired to run a large volume of paper material through equipment for processing such as printing, folding, addressing, labeling, packaging and many other purposes. Most feeders of this type include a generally vertical hopper with paper side guides wherein a stack of paper material is placed in a near vertical stack. The bottom sheet of the stack is typically pulled forward into the feeder by a series of feed rollers or feed belts. A sheet separator, or multiple sheet separators are placed typically over the feed belts or feed rollers and are adjusted vertically to allow a single sheet to be pulled through while inhibiting the movement of the remainder of the stack. Once the bottom sheet leaves the area of separation, the next sheet from the bottom of the stack is allowed to pass under the separators.
Sheet feeding machines developed to date have either fixed position feed rollers or fixed position feed belts. Most of these feeders are built to handle a variety of sizes of paper, therefore the position of these belts or rollers may not be optimum for every size sheet. In addition, most of these feeders, due to their lack of lateral adjustment of the belts and rollers, use side guides whose bottom edge extends to just above the feed belts or rollers, due to the fact that they must be positioned over the belts or rollers on small sheets. Additionally, these side guides only extend lengthwise through the feeder in the paper hopper area, limiting its ability to guide sheets once they leave the hopper.
Although the existing feeders of the prior art have moderate success running a variety of paper sizes and thicknesses, the lack of effective side guides causes a great deal of paper skewing or crooked feeding which causes many problems on the machine to which the feeder is attached.
The present invention relieves sheet skewing by using feed belts that are repositionable while the belts are being driven, and side guides that extend from the feed hopper through the entire length of the feeder. These guides also extend downward below the surface of the feed belts so sheet materials cannot slip underneath the guides as is common with existing feeders. Because the prior art feed belts did not offer lateral adjustment, the side guides could not extend below the surface of the feed belts.
Additionally, the prior art feeders typically utilize dual separators of fixed position, which are positioned over the top of firm feed rollers or belts. When set for thickness, these separators and the hard surface below them create a nip point which creates undo pressure on the sheet, causing jams, or force the top layer of a multi-layered piece to buckle backwards, causing jams. Furthermore, the prior art separators are made to move together, making no allowance for differences in thickness across the width of the sheet.
The present invention alleviates this problem by allowing independent positioning, both laterally and in a direction toward and away from the sheet being fed, of the sheet separators between the feed belts, so that they force separation of the stack by buckling the bottom sheet away from the stack. Since this area between belts does not present a hard surface level with the feed belts, this design does not create a high pressure nip point, thereby reducing jams.
On feeders of this prior art type, the sheet separators are usually made of a curved surface, typically a roller which is either stationary or rotates counter to the direction of the paper. These surfaces usually have a rubber or stone coating which creates extra friction to hold back the stack while the bottom piece is being fed. Although these surfaces generally work for a variety of paper types, sometimes they offer too much friction, either scratching the surface of glossy paper or causing jams by not allowing the bottom sheet through smoothly.
The present invention alleviates this problem by offering a separator tip that is simple to remove and replace, which can be replaced with tips of various materials that offer differing levels of friction.
Most standard feeder types of the prior art typically consist of a series of transport rollers and shafts that are supported by bearings on both ends. These bearings are typically mounted to the machine housing in recessed cutouts made specifically to house the bearings. Although this works well functionally it makes replacing the transport shafts, rollers or belts difficult, as the side frame, or transport assembly must be wholly removed from the feeder to perform this common service.
The present invention alleviates this problem by utilizing simple drop-in shafts, supported by a platform for the bearings to rest on, and capped off by an easily removable cap, which does not require disassembly of the side frame or transport assembly for service. The bearings on the end of the transport shafts are held in position by simple bearing blocks, from which the bearings and shafts can be lifted.
Finally, existing feeders typically include a paper support wedge, which is used to bias the stack of paper downward and forward toward the exit of the feeder. These wedges typically offer some adjustment for different paper sizes but do not extend past the rear end of the feeder, causing difficulty in running long paper.
The present invention remedies this by including a sheet support wedge with a reversible design and extended mounting bracket, which allows for short and long sheets.